1. ## probability values

Hello, I need help, which of the following represent valid probibility values?
0
100%
-0.8
0.001
thanks again

2. Originally Posted by mkcar
Hello, I need help, which of the following represent valid probibility values?
0
100%
-0.8
0.001
thanks again
when written in terms of a decimal, a valid probability value, call it P, ranges from $\displaystyle 0 \leq P \leq 1$

when written as a percentage: 0 % $\displaystyle \leq P \leq$ 100%

Note: when an event is certain, it has a probability of 1 or 100%, when an event is impossible, it has a probability of 0

3. Originally Posted by Jhevon
Note: when an event is certain, it has a probability of 1 or 100%, when an event is impossible, it has a probability of 0
But not the other way around. An event can be possible and still have probability 0, and not be certain and have probability 1.

RonL

4. How? By subjective probability from intuition, guesses, and estimates?

5. Originally Posted by rualin
How? By subjective probability from intuition, guesses, and estimates?
What are you refering to?

RonL

6. Originally Posted by CaptainBlack
But not the other way around. An event can be possible and still have probability 0, and not be certain and have probability 1.

RonL
Sorry, I forgot to quote. My question was, "How can it be that an event that's possible has a probability of 0 and one that is not certain has a probability of 1?"

7. Originally Posted by rualin
Sorry, I forgot to quote. My question was, "How can it be that an event that's possible has a probability of 0 and one that is not certain has a probability of 1?"
Suppose the lengths of rods are distributed normaly with mean mu and sd sigma.

Then it is possible for a rod to have length mu+signa/3, but the probability that it does is zero.

This is a toy construction but there are real cases where this can be important (fractal noise
comes to mind).

RonL